A. Field of the Invention
This invention relates to a novel process for preparing anisotropic oleum dopes of aromatic polyamides from which useful films, fibers and/or coatings may be shaped.
B. Description of the Prior Art
Anisotropic oleum dopes of aromatic polyamides, a process for preparing the same and the spinning thereof into fibers are described in the prior art, for example, in U.S. Pat. Nos. 3,671,542; 3,767,756; 3,801,528; 3,804,791; 3,819,587, 3,827,998; 3,836,498; 3,869,419; 3,869,429; and 3,969,420. According to the prior art process a diamine and diacid chloride are first reacted in a suitable organic solvent (e.g. a 2 to 1 mixture of hexamethylphosphoramide and N-methyl-2-pyrrolidone) at a low temperature (below 60.degree. C.) with stirring until a crumb-like solid consisting of polymer and solvent is obtained. The crumb is then thoroughly washed with water to remove the solvent therefrom and dried. Finally, appropriate amounts of the resulting dried polymer and oleum are combined with vigorous stirring until an anisotropic oleum dope is obtained. This process has several disadvantages. In the first place, the process requires the time consuming and expensive step of transferring the polyamide from one solvent to another. Also, the process requires the use of relatively expensive diacid chlorides.
It is an object of the present invention to provide a simpler, more economical and less time consuming process for preparing anisotropic oleum dopes of aromatic polyamides.
Other objects and advantages of the invention will become apparent from the following detailed description thereof.